1. Field of the Invention
The invention is directed to the field of power semiconductor modules and, more particularly, to power semiconductor modules having at least one fuse.
2. Description of the Related Art
Power semiconductor modules that are the point of departure for this invention are known for instance from German Patent Disclosure DE 103 16 355 B3. This reference discloses a power semiconductor module in the form of a half-bridge circuit arrangement, having a first and a second power switch. Each of these power switches is embodied as a parallel circuit of power transistors, each with an associated free-wheel diode. One first and one second power transistor with respective associated power diodes are each disposed on their own substrate.
In the above-referenced German Patent Disclosure, the substrates of the power semiconductor modules are embodied as insulating substrates, having an insulating body as substrate material and for electrical insulation relative to a base plate or a heat sink. These insulating bodies in the referenced disclosure are made up of an industrial ceramic, such as aluminum oxide or aluminum nitrite. A plurality of metal connecting tracks electrically insulated from one another are located on the insulating body, on its first main face oriented toward the interior of the power semiconductor module. The power semiconductor components are located on the tracks.
Usually, on its second main face remote from the interior of the power semiconductor module, the insulating body also has a metal layer of the same material and of the same thickness as that of the connecting tracks on the first main face. As a rule, however, this layer is not intrinsically structured, since it serves the purpose for instance of the soldered connection with a base plate. Both the connecting tracks and the metal layer of the second main face preferably comprise copper applied by the DCB (Direct Copper Bonding) method, and the copper then has a typical thickness of less than 1 mm.
The aforementioned power semiconductor modules of the prior art furthermore have load terminal elements for the two direct current terminals and for the at least one alternating current terminal. The load terminal elements connect external contacting means to associated connecting tracks on the substrate.
For internal insulation, power semiconductor modules in the prior art are potted to a level above the connecting elements with a potting compound having a high dielectric constant.
Modern power semiconductor components, especially power transistors, in the course of technological progress have an increasingly large current density. The power semiconductor components and the connecting tracks are typically connected by bond connections and in this case especially wire bond connections. In the prior art, various error scenarios in the use of power semiconductor modules are detected by suitable sensors in the power semiconductor module or in the circuitry of the power semiconductor module, and provisions to counter the errors, such as shutting off the power switches, are initiated by appropriate triggering electronics. However, error scenarios also occur that are not, or not completely, detected by this means. In those cases, an overcurrent may briefly flow and overload the bond wires within the interior of the power semiconductor module. This overcurrent melts at least one bond wire and, because of the existing inductances, the current flow arcs over the melted wire. In power semiconductor modules with a potting compound, this often leads to an explosion of the power semiconductor module due to the lack of compressibility of this potting compound in the short time interval and because of the internal pressure that thus builds up rapidly.